The present invention relates to a process for obtaining an object drawn from a softened material source having a chiralic structure and to a device for performing this process.
This drawn object has a random cross-section and is, for example, an optical fibre. This is the case which will be considered in a non-limitative manner throughout the remainder of the present patent application.
Monomodal fibres produced for telecommunications generally have a little linear birefringence and circular birefringence. As a result these fibres neither retain the linear polarization, nor the circular polarization.
It is possible to give the fibre a high level of linear birefringence by breaking the circular symmetry to the benefit of the planar symmetry.
It is also possible to consider a reverse method consisting of introducing a circular birefringence or rotatory power of a high level in order to retain the circular polarization.
One way of producing this circular polarization consists of subjecting the glass fibre to a static torsional stress, e.g. applied externally by twisting between its two ends. One effect of the twisting of the fibre is to introduce a circular birefringence therein.